A cargo subcommand for the client-side Web

This cargo subcommand aims to make it easy and convenient to build, develop and deploy client-side Web applications written in Rust.

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Patrons

This software was brought to you thanks to these wonderful people: * Embark Studios * Eduard Knyshov * Anselm Eickhoff * Ferran Pujol Camins * Isaac F Leonard * Johan Andersson * Martin Kavík * Stephen Sugden

Thank you!

Features

Currently it supports the following features:

• cargo web build - will build your project using one of Rust's three Web backends:
  • [asm.js] using Emscripten (when you pass --target=asmjs-unknown-emscripten; default)
  • [WebAssembly] using Emscripten (when you pass --target=wasm32-unknown-emscripten)
  • [WebAssembly] using Rust's native WebAssembly backend (when you pass --target=wasm32-unknown-unknown, requires Rust nightly)
• cargo web test - will run your tests either under:
  • Under a headless instance of Google Chrome (default)
  • Under [Node.js] (when you pass --nodejs)
• cargo web start - will build your project, start an embedded webserver and will continuously rebuild it if necessary; supports automatic reloading with --auto-reload.
• cargo web deploy - will build your project and emit all of the necessary files so that you can easily serve them statically.
• Will automatically download and install Emscripten for you (if necessary) on the following platforms:
  • Linux x86-64
  • Linux x86
• Will automatically garbage-collect your WebAssembly artifacts.

It's also highly recommended that you check out the [stdweb] crate if you want to interact with the JavaScript world in your project. (In fact, cargo-web is what makes it possible to use stdweb's js! macro on Rust's native WebAssembly backend.)

Installation

$ cargo install cargo-web

To upgrade:

$ cargo install --force cargo-web

Or clone and build with $ cargo build --release then place in your $PATH.

On Linux the installation can fail with a message that it can't find OpenSSL, in which case you most likely need to install the -dev package for OpenSSL from your distribution's repositories. (On Ubuntu it's called libssl-dev.)

Web.toml

cargo-web has its own configuration file which you can put next to cargo's [Cargo.toml].

Here's an example configuration showing every supported key:

```toml

The default value of --target used when building this crate

in cases where it's not specified on the command line.

default-target = "wasm32-unknown-unknown"

This will prepend a given JavaScript file to the resulting .js artifact.

You can put any initialization code here which you'd like to have executed

when your .js file first loads.

#

This accepts either a string (as shown here), or an array of strings,

in which case it will prepend all of the specified files in their

order of appearance.

prepend-js = "src/runtime.js"

[cargo-web]

Asserts the minimum required version of cargo-web necessary

to compile this crate; supported since 0.6.0.

minimum-version = "0.6.0"

These will only take effect on *-emscripten targets.

[target.emscripten]

You can have a target-specific prepend-js key.

prepend-js = "src/emscripten_runtime.js"

This will enable Emscripten's SDL2 port. Consult Emscripten's documentation

for more details.

link-args = ["-s", "USE_SDL=2"]

You can also specify the target by its full name.

[target.wasm32-unknown-unknown] prepend-js = "src/native_runtime.js" ```

If you use any external crates which have a Web.toml then cargo-web will load it and use it.

A few restrictions concerning the Web.toml:

• You can't have overlapping prepend-js keys. You can either define a single global prepend-js, or multiple per-target ones.
• The link-args currently can't have any spaces in them.
• The order in which cargo-web will process the Web.toml files from multiple crates is deterministic yet unspecified. This means that you shouldn't depend on this order in any way.

Static files

Any static files you'd like to have served when running cargo web start or deployed when running cargo web deploy can be put in a directory called static in the root of your crate. No static artifacts are required by default; an index.html file will be automatically generated for you if it's missing. You can, of course, put your own static/index.html file, in which case it will be used instead of the autogenerated one.

Detecting cargo-web during compilation

If during compilation you'd like to detect that your project is being built with cargo-web you can check the COMPILING_UNDER_CARGO_WEB environment variable, which will be set to 1.

Using cargo-web on Travis

Precompiled binaries

You can use the following script to download and install the latest cargo-web:

```shell CARGOWEBRELEASE=$(curl -L -s -H 'Accept: application/json' https://github.com/koute/cargo-web/releases/latest) CARGOWEBVERSION=$(echo $CARGOWEBRELEASE | sed -e 's/."tag_name":"([^"])".*/1/') CARGOWEBURL="https://github.com/koute/cargo-web/releases/download/$CARGOWEBVERSION/cargo-web-x86_64-unknown-linux-gnu.gz"

echo "Downloading cargo-web from: $CARGOWEBURL" curl -L $CARGOWEBURL | gzip -d > cargo-web chmod +x cargo-web

mkdir -p ~/.cargo/bin mv cargo-web ~/.cargo/bin ```

Running tests under headless Chrome

By default cargo web test will run your tests under headless Chrome. To be able to use this on Travis you need to add something like this to your .travis.yml:

yaml addons: chrome: stable

Changelog

• 0.6.22
  • Running tests through Chrome should now work out-of-box on macOS
  • The deploy subcommand can now be told where to deploy using the -o/--output parameter
  • Static files with spaces in their names are now properly served
  • Access-Control-Allow-Origin: * is now always sent by the embedded webserver
  • Debug builds on wasm32-unknown-unknown are now supported provided a recent enough stdweb is used
• 0.6.21
  • Emscripten was updated to 1.38.19; the Emscripten-based targets should now work again on nightly
  • Broken output redirection in the test runner is now fixed
  • The generated JS snippets and imports under wasm32-unknown-unknown are now sorted
  • Compatibility with really old nightlies was removed for wasm32-unknown-unknown
• 0.6.20
  • Installation through cargo install should now work again
  • Most of the dependencies were updated to newer versions
  • deploy should not panic when it doesn't find a valid target
• 0.6.19
  • cargo install should now compile instead of failing in some environments
  • Minimum required Rust version is now 1.26.2
• 0.6.18
  • Default index.html doesn't have a newline before its doctype anymore
• 0.6.17
  • OpenSSL is now vendored; this should fix the compilation in some environments
  • Minimum required Rust version is now 1.25.0
• 0.6.16
  • The runtime for wasm32-unknown-unknown now uses WebAssembly.instantiateStreaming when available
  • Running tests under headless Chromium is now supported for the wasm32-unknown-unknown target
  • Color codes are no longer emitted when the output of cargo-web is redirected
  • Improved coloring; a lot more messages should now be colored
  • Initial experimental support for asynchronous tests

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.